To be honest, no vegetable will perform all that well in a very weedy environment because the weeds compete against the desired plant for water, sun, nutrients and so on. Although sweet potatoes can eventually grow enough to shade out weeds, they must initially be grown in a weed-free area until well-established. Unfortunately, this is true for all the vegetables I can think of. In terms of low maintenance, sweet potatoes require careful planting and ridging and must be harvested and handled gently to be of good keeping quality. Thinking of other vegetables, in my experience pumpkins are pretty easy to grow. You might also consider some of the simple weed control measures such as mulching to help cut down on the weeds, too.